INFLUENCE OF CHEMICAL CONSTITUTION ON THE ADSORPTION OF DYESTUFFS BY THE INSOLUBLE PART OF THE HEAT-DEHYDRATED GUM ARABIC

Gum arabic becomes partly insoluble in water when heated to 165°-170° and the insoluble part could adsorb only basic dyes irreversibly, exchanging Ca ions for basic dye ions ; Freundlich’s isotherm is followed in case of malachite green only. Congo red though being an acid dye is adsorbed from very low concentrations. Presence of sodium chloride in the dyeing bath prevents the adsorption of basic dyes.